If someone attacks a server this way, the server would not log the attack – the compromise is silent.

So what does this all mean?

If you operate a web site protected by HTTPS, with the S — SSL — implemented using the OpenSSL code, you obviously have to patch immediately.

Anything on affected web servers may have been compromised. The most worrying bit is the server’s private SSL certificate. Why is that a problem? Because someone who steals that private SSL certificate could subsequently impersonate your web site without alerting users visiting his fake server that they are not communicating with the legitimate site. This is a man-in-the-middle attack.

If you sign into a web site that has been compromised this way, then a man-in-the-middle attack such as the above may have been used to steal your password (in plaintext – it does not matter how good your password was). This is especially problematic in public spaces like coffee shops or airports, where a man-in-the-middle attack would be much easier to carry out than – say – when you sign into systems from your home or office.

A server that was compromised might also leak password data. Very few systems store plaintext passwords these days, and large web sites would not store password hashes on the front-end web server anyways, so this is mainly a concern if you sign into a smallish web site, which stores password hashes locally on the web server, and if your password was a fairly easy to guess one.

Do we know about anyone who has actually been “hacked” this way? The short answer is NO. There is a great risk of compromise here, but I have not heard of any actual compromised web sites, server certificates or passwords. Be careful, but don’t panic, in other words.

How are the media handling this? As you might expect, with lots of sensational and misleading nonsense. I read an article in the local newspaper that was particularly shocking — i.e., the quality and accuracy of the coverage was about as poor as I’ve seen in recent years. If you want a chuckle, read this:

Do you operate an affected web site? Patch your OpenSSL library and get/install a fresh certificate, because there is a risk that your old cert was compromised. Good business for the certificate authorities here.

Do you sign into an affected web site? (You should assume yes, since OpenSSL is so common). Wait a few days and change your password. Make sure your web browser checks for revoked certificates. On my Firefox instance, I checked about:config and found that app.update.cert.checkAttributes was true. That’s good.

Addendum: as one might expect, the always-brilliant XKCD explains the vulnerability perfectly: